Andrew W. Gardner

The Clinical Utility of a Six-Minute Walk Test in Peripheral Arterial Occlusive Disease Patients

OBJECTIVES: To determine the test‐retest reliability of the distance covered and the steps taken to complete a 6‐minute walk test by peripheral arterial occlusive disease (PAOD) patients with intermittent claudication. To determine the relationship between the total distance and steps covered during the 6‐minute walk test and clinical measures of PAOD severity.

Effects of exercise rehabilitation on endothelial reactivity in older patients with peripheral arterial disease

Peripheral arterial disease (PAD) is a major cause of morbidity and mortality. Endothelial function, which is a measure of vascular health, is impaired in patients with PAD. We examined the effects of 6 months of aerobic exercise rehabilitation on brachial artery endothelial function, assessed using high-frequency ultrasonography, and calf blood flow in 19 older PAD patients (age 69 +/- 1 years, mean +/- SEM) with intermittent claudication (ankle to brachial artery index of 0.73 +/- 0.04). After exercise, the time to onset of claudication pain increased by 94%, from 271 +/- 49 to 525 +/- 80 seconds (p <0.01), and the time to maximal claudication pain increased by 43%, from 623 +/- 77 to 889 +/- 75 seconds (p <0.05). Exercise rehabilitation increased the flow-mediated brachial arterial diameter by 61%, from 0.18 +/- 0.03 to 0.29 +/- 0.04 mm (p <0.005), as well as the relative change in brachial arterial diameter from the resting state by 60%, from 4.81 +/- 0.82% to 7.97 +/- 1.03% (p <0.005). Maximal calf blood flow (14.2 +/- 1.0 vs 19.2 +/- 2.0 ml/100 ml/min; p = 0.04), and postocclusive reactive hyperemic blood flow (9.8 +/- 0.8 vs 11.3 +/- 0.7 ml/100 ml/min; p = 0.1) increased 35% and 15%, respectively. In conclusion, exercise rehabilitation improved ambulatory function, endothelial-dependent dilation, and calf blood flow in older PAD patients with intermittent claudication.

Efficacy of Quantified Home-Based Exercise and Supervised Exercise in Patients With Intermittent Claudication A Randomized Controlled Trial

Background— This prospective, randomized, controlled clinical trial compared changes in exercise performance and daily ambulatory activity in peripheral artery disease patients with intermittent claudication after a home-based exercise program, a supervised exercise program, and usual-care control. Methods and Results— Of the 119 patients randomized, 29 completed home-based exercise, 33 completed supervised exercise, and 30 completed usual-care control. Both exercise programs consisted of intermittent walking to nearly maximal claudication pain for 12 weeks. Patients wore a step activity monitor during each exercise session. Primary outcome measures included claudication onset time and peak walking time obtained from a treadmill exercise test; secondary outcome measures included daily ambulatory cadences measured during a 7-day monitoring period. Adherence to home-based and supervised exercise was similar (P=0.712) and exceeded 80%. Both exercise programs increased claudication onset time (P<0.001) and peak walking time (P<0.01), whereas only home-based exercise increased daily average cadence (P<0.01). No changes were seen in the control group (P>0.05). The changes in claudication onset time and peak walking time were similar between the 2 exercise groups (P>0.05), whereas the change in daily average cadence was greater with home-based exercise (P<0.05). Conclusions— A home-based exercise program, quantified with a step activity monitor, has high adherence and is efficacious in improving claudication measures similar to a standard supervised exercise program. Furthermore, home-based exercise appears more efficacious in increasing daily ambulatory activity in the community setting than supervised exercise. Clinical Trial Registration— URL: http://www.ClinicalTrials.Gov. Unique identifier: NCT00618670.

Endothelial reactivity and cardiac risk factors in older patients with peripheral arterial disease

Peripheral arterial disease (PAD) is a major cause of morbidity and mortality. Endothelium-dependent vasoreactivity, which is advocated as a measure of vascular health, is impaired in persons with cardiac risk factors and coronary artery disease. Few studies have examined the degree of endothelial dysfunction in patients with PAD. Using high-resolution external vascular ultrasound, we measured brachial artery diameter and flow at rest, and in response to reactive hyperemia (flow-mediated dilation) in 50 older patients (age 69 +/- 1 year) with PAD (ankle-to-brachial artery index of 0.67 +/- 0.03), and 50 age-matched non-PAD patients. Coronary artery disease was more prevalent in PAD than in non-PAD patients (40% vs 4%, p <0.001). Systolic blood pressure (153 +/- 4 vs 141 +/- 3 mm Hg, p <0.01), fasting glucose (129 +/- 6 vs 109 +/- 5 mg/dl, p <0.001), and pack-years smoked (54 +/- 7 vs 25 +/- 3, p <0.01) were higher in the PAD than in non-PAD patients. There were no differences in baseline brachial artery diameter, blood velocity, or flow between the 2 groups. However, the 1-minute postocclusion percent change in diameter (6.5 +/- 0.7% vs 9.8 +/- 0.7%, p <0.001) and the change in diameter (0.22 +/- 0.02 vs 0.33 +/- 0.02 mm, p <0.001) were lower in PAD than in non-PAD patients, suggesting impaired endothelium-dependent dilation. The postocclusion hyperemic velocity and blood flow were also lower in PAD than in non-PAD patients. In multiple regression analyses the low-density lipoprotein-to-high-density lipoprotein cholesterol ratio, elevated fasting glucose, and high systolic blood pressure were independent predictors of percent change in brachial artery diameter (r2 = 0.37, p <0.001). Thus, older patients with PAD had impaired endothelial dependent vasodilation compared with controls that was associated with the presence of cardiac risk factors. The effect of cardiac risk factor intervention on endothelial function in patients with PAD remains to be determined.

Physical activity is a predictor of all-cause mortality in patients with intermittent claudication.

OBJECTIVEnWe examined whether all-cause mortality was predicted by physical activity level in peripheral arterial disease (PAD) patients limited by intermittent claudication.nnnMETHODSnThis retrospective, natural history follow-up study determined survival status of each patient. Patients with stable symptoms of intermittent claudication were evaluated in the Geriatrics, Research, Education, and Clinical Center at the Maryland Veterans Affairs Health Care System (MVAHCS) at Baltimore between 1994 and 2002, and were classified into a physically sedentary group (n = 299) or a physically active group (n =135), and followed in 2004 using the Social Security Death Index.nnnRESULTSnMedian follow-up was 5.33 years (range = 0.25 to 8.33 years) for the physically active group, and 5.0 years (range = 0.17 to 8.5 years) for the sedentary group. At follow-up, 108 patients (24.9%) had died, consisting of 86 (28.8%) in the sedentary group and 22 (16.3%) in the active group. Unadjusted risk of mortality was lower (P = .005) in the physically active group (hazard ratio [HR] = 0.510, 95% CI = 0.319 to 0.816). In multivariate Cox proportional hazards analysis, age (HR = 1.045, 95% CI = 1.019 to 1.072, P < 0.001), body mass index (BMI) (HR = 0.943, 95% CI = 0.902 to 0.986, P = 0.009), ankle-brachial index (ABI) (HR = 0.202, 95% CI = 0.064 to 0.632, p = 0.006), and physical activity status (HR = 0.595, 95% CI = 0.370 to 0.955, P = .031) were predictors of mortality.nnnCONCLUSIONnPatients limited by intermittent claudication who engage in any amount of weekly physical activity beyond light intensity at baseline have a lower mortality rate than their sedentary counterparts who perform either no physical activity or only light-intensity activities. The protective effect of physical activity persists even after adjusting for other predictors of mortality, which include age, ABI, and BMI.

Optimal exercise program length for patients with claudication

BACKGROUNDnThis prospective, randomized controlled clinical trial determined whether an optimal exercise program length exists to efficaciously change claudication onset time (COT) and peak walking time (PWT) in patients with peripheral artery disease and claudication.nnnMETHODSnThe study randomized 142 patients to supervised exercise (n = 106) or a usual care control group (n = 36), with 80 completing the exercise program and 27 completing the control intervention. The exercise program consisted of intermittent walking to nearly maximal claudication pain 3 days per week. COT and PWT were the primary outcomes obtained from a treadmill exercise test at baseline and bimonthly during the study.nnnRESULTSnAfter exercise, changes in COT (P < .001) and PWT (P < .001) were consistently greater than changes after the control intervention. In the exercise program, COT and PWT increased from baseline to month 2 (P < .05) and from months 2 to 4 (P < .05) but did not significantly change from months 4 to 6 (P > .05). When changes were expressed per mile walked during the first 2 months, middle 2 months, and final 2 months of exercise, COT and PWT only increased during the first 2 months (P < .05).nnnCONCLUSIONSnExercise-mediated gains in COT and PWT occur rapidly within the first 2 months of exercise rehabilitation and are maintained with further training. The clinical significance is that a relatively short 2-month exercise program may be preferred to a longer program to treat claudication because adherence is higher, costs associated with personnel and use of facilities are lower per patient, and more patients can be trained for a given amount of personnel time and resource utilization.

The Relationship Between Lower Extremity Functional Strength and Severity of Peripheral Arterial Disease

The purposes of this study were to (1) determine if peripheral arterial disease (PAD) severity is related to deficits in lower extremity functional strength, (2) identify covariates that might affect the relationship between lower extremity functional strength and severity of PAD, and (3) determine if the relationship between lower extremity functional strength and severity of PAD still persists after statistically controlling for significant covariates. A total of 144 patients were grouped into tertiles according to disease severity. Patients having an ankle-brachial index (ABI) of 0.76 to 0.90 were classified as having mild PAD (high ABI group), 0.51 to 0.75 classified as having moderate PAD (moderate ABI group), and 0.36 to 0.50 as having severe PAD (low ABI group). Lower extremity functional strength was assessed using the chair-stand test where the time to complete 5 consecutive stand-to-sit transfers was recorded. Patients were also characterized on ambulatory function and clinical characteristics. The moderate ABI group took significantly (p<0.05) less time (13.49 ±0.49 s) to complete the chair-stand test than the low ABI group (15.86 ±0.63 s). Both daily physical activity level and total 6-minute walk distance were identified as significant covariates (p<0.05) of lower extremity functional strength. After controlling for daily physical activity level and total 6-minute walk distance, no significant differences (p>0.05) in the time to complete the chair-stand test existed between the ABI groups. These findings indicate that the greater impairment in lower extremity functional strength in patients with severe PAD is explained by their lower physical activity level and poorer overall walking ability.

Unilateral impairment of leg blood flow in chronic stroke patients.

Background: Previous studies comparing paretic limb blood flow with the unaffected limb have been contradictory and have often omitted comparisons of peak reactive hyperemic flow. Our objective was to perform bilateral measurements of resting and reactive hyperemic blood flow in the lower legs of chronic (>6 months) stroke patients. A secondary purpose was to determine the extent to which any unilateral changes in limb blood flow were a function of decreases in lean tissue mass on the affected side. We hypothesized that the chronic hemiparesis accompanying ischemic stroke creates an altered metabolic environment in the tissues of the affected side that ultimately impairs vasomotor function. Methods: The study used a single-visit cross-sectional design. All tests were performed at the Baltimore VA Medical Center. Nineteen chronic hemiparetic stroke patients (15 male, 4 female) who had mild to moderate hemiparetic gait after ischemic stroke were recruited for observation. Bilateral measurements of resting and reactive hyperemic blood flow were made using venous occlusion strain gauge plethysmography. Paired t-tests were used for the between leg comparison. Regression analysis and analysis of covariance were utilized to determine the strength of the relationship between lower leg lean tissue mass and blood flow. Results: Resting and reactive hyperemic blood flows were significantly reduced in the paretic compared with the non-paretic limb (32 and 35%, respectively, p < 0.001). Lean tissue mass was also significantly lower in the affected limb (p < 0.01). However, neither resting nor reactive hyperemic blood flows were significantly correlated with lower leg lean tissue mass by dual energy X-ray absorptiometry. The difference in blood flow between limbs remained after covarying for lean tissue mass. Conclusion: Hemiparesis causes impairments in vasomotor function under both resting and hyperemic conditions that are independent of the muscle atrophy on the affected side.

GENDER DIFFERENCES IN DAILY AMBULATORY ACTIVITY PATTERNS IN PATIENTS WITH INTERMITTENT CLAUDICATION

OBJECTIVESnTo compare the pattern of daily ambulatory activity in men and women with intermittent claudication, and to determine whether calf muscle hemoglobin oxygen saturation (StO2) is associated with daily ambulatory activity.nnnMETHODSnForty men and 41 women with peripheral arterial disease limited by intermittent claudication were assessed on their community-based ambulatory activity patterns for 1 week with an ankle-mounted step activity monitor and on calf muscle StO2 during a treadmill test.nnnRESULTSnWomen had lower adjusted daily maximal cadence (mean±SE) for 5 continuous minutes of ambulation (26.2±1.2 strides/min vs 31.0±1.2 strides/min; P=.009), for 1 minute of ambulation (43.1±0.9 strides/min vs 47.2±0.9 strides/min; P=.004), and for intermittent ambulation determined by the peak activity index (26.3±1.2 strides/min vs 31.0±1.2 strides/min; P=.009). Women also had lower adjusted time to minimum calf muscle StO2 during exercise (P=.048), which was positively associated with maximal cadence for 5 continuous minutes (r=0.51; P<.01), maximal cadence for 1 minute (r=0.42; P<.05), and peak activity index (r=0.44; P<.05). These associations were not significant in men.nnnCONCLUSIONnWomen with intermittent claudication ambulate slower in the community setting than men, particularly for short continuous durations of up to 5 minutes and during intermittent ambulation at peak cadences. Furthermore, the daily ambulatory cadences of women are correlated with their calf muscle StO2 during exercise, as women who walk slower in the community setting reach their minimum calf muscle StO2 sooner than those who walk at faster paces. Women with intermittent claudication should be encouraged to not only walk more on a daily basis, but to do so at a pace that is faster than their preferred speed.

The Effect of Cigarette Smoking Status on Six-Minute Walk Distance in Patients with Intermittent Claudication

The purposes of the study were threefold: (1) to compare 6-minute walk performance as a measure of exercise tolerance among three different groups of peripheral arterial occlusive disease (PAOD) patients with intermittent claudication—current smokers, former smokers, and patients who have never smoked; (2) to identify important covari ates that might affect the relationship between smoking and exercise in the PAOD popu lation ; (3) to determine whether differences among the three groups in 6-minute walk performance persist after statistically controlling for the significant covariates. Recruited into the study were 415 PAOD patients with intermittent claudication between the ages of 42 and 88 years. The self-reported smoking status consisted of 182 current smokers, 196 former smokers, and 37 patients who had never smoked. The authors recorded 6- minute walk distance, a reliable measurement of exercise tolerance in PAOD patients, as well as age, body composition, self-reported ambulatory function, self-reported physical activity, and standard peripheral hemodynamics. Nonsmokers walked significantly farther (413 ± 14 m; mean ±standard error) and took more steps (665 ± 14 steps) than either current (352 ±7 m; 563 ±9 steps) or former smokers 370 ±7 m; 600 ±8 steps) (p<0.05). The nonsmokers had a higher ankle-brachial index (ABI) value (0.70 ±0.03) than patients who actively smoked 0.62 ± 0.01 (p<0.03); the authors observed an inverse relationship between smoking history and self-reported physical activity (WIQ Distance Score: nonsmokers 51 ±6%, former smokers 38 ±3%, and smokers 32 ±2%) (p<0.01). From a multivariate perspective, ABI, physical activity, and perceived walking ability were the only independent predictors of 6-minute walk distance. Differences in the adjusted 6-minute walk distance among the nonsmokers (388 ± 13 m), current smokers (359 ±6 m), and former smokers (368 ±6 m) no longer remained after controlling statis tically for these covariates. The findings suggest that 6-minute walk distance is a sensitive measure to detect differences in submaximal exercise performance between smoking and nonsmoking PAOD patients with intermittent claudication. Moreover, the group differ ence in the 6-minute walk distance is explained by group differences in walking percep tion, PAOD severity, and physical activity level.